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Mathematical Modeling of the Pneumatic Conveying of Semicoke in the Pilot Plant of Coal Topping

Author: ZhaoDanNi
Tutor: ZhaoGuangBo
School: Harbin Institute of Technology
Course: Thermal Power Engineering
Keywords: Coal topping Co-generation Pneumatic conveying Semicoke
CLC: TQ022.3
Type: Master's thesis
Year: 2007
Downloads: 89
Quote: 2
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Abstract

The coal topping technology is to realize flash pyrolysis at relatively low temperature and extract combustible gas, liquid fuel and fine chemicals from coal without addition of catalysts or H2. In the process, desulfurization and denitrific-ation can be achieved and oil, gas, heat and electricity can be co-generated simultaneously.Pneumatic conveying technology is to convey materiel by negative pressure or positive pressure. The semicoke is conveyed in this way because it is efficient, simple for operation, Also, the high temperature materiel can be conveyed because it is air tight. The temperature of semicoke form rapid separator is higher than its ignition point. So the semicoke is likely to combust with a flock of heat giving out in the transportation with the energy loss and high temperature danger as a result. It is very helpful for operation of coal topping system to predict the velocity, pressure and combustion in the pneumatic conveying of semicoke.The one-dimension model of the pneumatic conveying of semicoke and ash was set up. The momentum equation bases on the analysis of the power on solids and the Newton Second Law. The reaction includes the separating out and combusting of residual volatile, the combusting of coke, the heterogeneous reactions of coke with O2 and CO2 and the homogeneous reactions involving CO and O2.The heat transfer between semicoke and ash is ignored. The convection and radiation heat transfer between gas and solid and the heat of combustion is concerned. The additional pressure method is used to calculate the pressure loss.The mathematical modeling of the pneumatic conveying of semicoke in the pilot plant of coal topping is calculated. With the result of three conditions in that the semicoke is conveyed by preheated air, cold air and smoke respectively analyzed, It is found that the temperature and gas velocity are both high. The pressure loss and abrasion is excessive as a result. The temperature, gas velocity and pressure loss in the condition using air are all higher by using air than using smoke. The combustion of coke in the process can be ignored because of the short settling time and lack of oxygen.Secondly, the effect of characteristic parameters change is discussed. The results indicate that the more residual volatile exists in semicoke, the higher temperature and pressure loss is in exit. The longer settling time is, the higher temperature is. The volatile has burned out when the settling time is longer than 0.6 seconds. The temperature in exit increases linearly with the air’s initial temperature in the range of 20～180℃. The various diameters of the pipeline are used is used to reduce the power consume and abrasion. Along with the diameter of equal-diameter part increase, the pressure loss falls. The immoderate diameter of equal-diameter part will reduce the pipeline capacity.

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CLC: > Industrial Technology > Chemical Industry > General issues > Chemical processes ( physical processes and physical and chemical processes ) > Delivery of materials > The solids conveying process
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